The ground wire you left off , may be for the generator , hooking that wire up would be the first thing to try.
Then , you'll have to check for battery volts at the gen set , on mine the cables are at the bottom rear of the generator.
The click you hear is an indication of either an internal problem ( starter ) or low voltage supply to the generator.
Has the coach been plugged into shore power ? Are both chassis and coach batteries showing good charge?
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.